Ever more stringent regulations regarding permissible pollutant emissions by motor vehicles fitted with internal combustion engines make it necessary to keep the pollutant emissions as low as possible during operation of the internal combustion engine. One of the ways in which this can be done is by reducing the emissions which occur during the combustion of the air/fuel mixture in the relevant cylinder of the internal combustion engine. Another is to use exhaust gas handling systems in internal combustion engines which convert the emissions which are generated during the combustion process of the air/fuel mixture in the relevant cylinder into harmless substances. Catalytic converters are used for this purpose which convert carbon monoxide, hydrocarbons and nitrous oxide into harmless substances. Both the explicit influencing of the generation of the pollutant emissions during the combustion and also the conversion of the pollutant components with a high level of efficiency by an exhaust gas catalytic converter require a very precisely set air/fuel ratio in the respective cylinder.
In particular it is also advantageous for the catalytic converter to be quickly ready for operation soon after the internal combustion engine has been started as regards avoiding pollutant emissions, since it is precisely in the first operating phase of the internal combustion engine that increased pollutant emissions are generated because the operating temperature of the internal combustion engine is still low. For this purpose, the practice is known of injecting fuel into the combustion chamber of the respective cylinder of the internal combustion engine such that this essentially passes into the exhaust gas tract uncombusted and oxidizes there, so that the thermal energy thus released leads to a rapid heating up of the catalytic converter and thereby to a rapid readiness for operation of the catalytic converter.
Linear closed-loop Lambda control with a linear Lambda probe which is arranged upstream from an exhaust gas catalytic converter and a binary Lambda probe which is arranged downstream of the exhaust gas catalytic converter is known from the German textbook, “Handbuch Verbrennungsmotor”, published by Richard von Basshuysen, Fred Schäfer, 2nd edition, Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, Pages 559-561. A Lambda setpoint value is filtered by means of a filter which takes account of gas delay times and the sensor behavior. The Lambda setpoint value filtered in this way is the guide value of a PII2D Lambda control, of which the manipulated variable is an injection amount correction.